This invention relates to a new topical composition for inhibiting mammalian hair growth. It also relates to a method of inhibiting hair growth by applying a topical composition according to this invention to the skin.
In U.S. Pat. No. 4,720,489 it is disclosed that the topical application of a composition comprising an ornithine decarboxylase ("ODC") inhibitor will inhibit hair growth, including beard hair growth. A particularly advantageous ODC inhibitor for use in this application is 2-(difluoromethyl)-2,5-diaminopentanoic acid, also identified as .alpha.-(difluoromethyl)ornithine ("DFMO"). This patent demonstrates the effectiveness of ODC inhibitors for inhibiting hair growth by measuring changes in flank organ hair mass in adult male hamsters treated with ethanol solutions of such compounds. The patent also generally proposes the possible incorporation of ODC inhibitors in cosmetic formulations such as skin lotions and creams, but the effectiveness of such proposed formulations and their stability and aesthetic attributes are unknown. Since DFMO is a highly ionic material, it would tend to destabilize emulsion systems and would be difficult to formulate in such systems, particularly at higher dosage levels necessary to achieve maximum efficacy.
In U.S. Pat. No. 5,095,007, U.S. Pat. No. 5,096,911, and U.S. Pat. No. 5,132,293, additional hair growth inhibitors are disclosed which are completely unrelated to the aforementioned ODC inhibitors. However, each of these patents discloses a water-ethanol vehicle for delivering the active compound. The vehicle comprises 68% water, 16% ethanol, 5% propylene glycol, 5% dipropylene glycol, 4% benzyl alcohol, and 2% propylene carbonate. This vehicle is not aesthetically pleasing or easy to use since it is very runny and feels wet and tacky. Moreover, the efficacy of the active material in this vehicle may not be optimum even though the vehicle contains two known penetration enhancers, namely benzyl alcohol and propylene carbonate.
It is an object of the present invention to provide a topical composition for inhibiting hair growth which is stable, highly efficacious and aesthetically pleasing.